Electron beam chemistry in solid films of poly(vinyl alcohol): Exposures under vacuum and under N2 at atmospheric pressure; irradiation monitored by using infrared spectroscopy
Abstract
Thin films of poly(vinyl alcohol) (PVA) were exposed to a 25-kV electron beam under high vacuum conditions and to a 175-kV electron beam at atmospheric pressures of N2. The decomposition of PVA by the electron beam sequentially formed materials that had polyketone- and polyethylene-like structures, respectively. Contrary to previous reports we show that the ketone groups formed as a result of the electron beam exposure are not due to an oxidation step by molecular oxygen. Damage cross sections for the electron beam decomposition (at 25 kV) were determined for PVA and the polyketone, and G values were determined for decomposition (at 25 kV) were determined for PVA and the polyketone, and G values were determined for decomposition of -OH groups and formation of ketone functional groups. Special attention was given to correct calculation of absorbed dose in each type of exposure and the influence of refractive index change on band intensity versus concentration. A mechanism is proposed for the electron beam induced reaction that encompasses data already in the literature and new information in the present report. © 1990 American Chemical Society.